| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | -1 |
| 3 | 7 |
| 4 | -20 |
| 5 | 125 |
| 6 | -721 |
| 7 | 5731 |
| 8 | -49440 |
| 9 | 505529 |
| 10 | -5716921 |
| 11 | 72560255 |
| 12 | -1009426340 |
| 13 | 15366052533 |
| 14 | -253286287801 |
| 15 | 4501151653979 |
| 16 | -85717611666720 |
| 17 | 1742059862631537 |
| 18 | -37625735499057361 |
| 19 | 860703388428813303 |
[0,1,-1,7,-20,125,-721,5731,-49440,505529, -5716921,72560255,-1009426340,15366052533, -253286287801,4501151653979,-85717611666720, 1742059862631537,-37625735499057361, 860703388428813303] |